The overall goals of this research are first, elucidation of the molecular mechanisms of an ion pump whose genes are natural components of a bacterial resistance plasmid, and second, the role of this transport system in bacterial resistance to antibiotics and toxic compounds. The clinical resistance plasmid R773 carries the arsenical resistance (ars) operon, which produces resistance to arsenate, arsenite, and antimonite. The operon encodes an oxyanion-translocating ATPase which functions as an ATP-coupled extrusion pump for the toxic oxyanions. In this collaborative project analysis will be extended to determine the energetics of this novel anion pump, with the specific aim of determination of the mechanism of energy coupling. The laboratory of Professor V.P. Skulachev pioneered the methodology for the measurement of membrane potentials and ion fluxes in mitochondria, submitochondrial particles, bacteria and bacterial membrane vesicles. Professor Skulachev is uniquely qualified to perform these collaborative studies. While plasmid-mediated antibiotic and heavy metal resistances which are due to energy-dependent efflux systems may be wide spread in nature, anion pumps appear to be rather rare. The arsenical efflux system provide a good model system for the study of transmissible bacterial antibiotic resistances. The plasmid encoded ars system also provides a bacterial model for the study of multidrug resistance in mammalian cells. The Ars ATPase exhibits structural and functional similarity to the P-glycoprotein, the protein which produces multiple drug resistance in tumor cells.